1. Field
The present disclosure relates to a multi-chip module (MCM) that accommodates semiconductor chips. More specifically, the present disclosure relates to an MCM that includes a vertical stack of semiconductor chips with inter-chip optical interconnects.
2. Related Art
Engineers have recently proposed using a multi-chip module (MCM) (which is sometimes referred to as a ‘macro-chip’) to integrate a collection of semi-conductor chips. This MCM offers unprecedented computational density, energy efficiency, bisection bandwidth and reduced message latencies. These characteristics are obtained by photonically interconnecting multiple silicon chips into a logically contiguous piece of silicon. This interconnection technique facilitates integration of computer system components, such as: multi-core, multi-threaded processors, system-wide interconnects and dense memories.
As shown in FIG. 1, in one configuration of MCM 100, island chips 110 and bridge chips 112, are arranged in a two-dimensional, multi-tiered array. In this MCM, an upward-facing island chip (such as island chip 110-1) in the lower tier in MCM 100 is coupled to a downward-facing bridge chip (such as bridge chip 112-1) in the upper tier. In particular, in the regions where these chips overlap, communication occurs via proximity communication of optical signals (which is referred to as ‘optical proximity communication’ or OPxC).
Because the optical proximity communication occurs between active surfaces, island chips 110 and bridge chips 112 need to face each other. Consequently, the number of chip layers in MCM 100 is typically limited to two. However, this limitation constrains potential improvements in the device density and chip functionality that can be obtained, and thus, the performance, form factor and cost of MCM 100.
Hence, what is needed is an MCM without the above-described limitations.